1. Field of the Invention
The present invention relates to actuator elements that bend when voltage is applied and input apparatuses.
2. Description of the Related Art
FIGS. 13A and 13B are conceptual diagrams (section views) of an input apparatus for explaining problems in the past.
An input apparatus 1 illustrated in FIG. 13A has actuator elements 2, a base member 3, fixing units 4, a key top 5, and a housing 6.
As illustrated in FIG. 13A, the actuator elements 2 are fixed to and are supported by the fixing units 4 in a cantilever form. Each of the actuator elements 2 may have an electrolytic layer and a pair of electrode layers provided on both sides of the electrolytic layer in the direction of thickness, for example. When voltage is applied to the pair of electrode layers on the fixed end, the actuator element bends upward, as illustrated in FIG. 13A.
The actuator element 2 has a lower modulus of elasticity and lower rigidity than a piezoelectric ceramic or a shape-memory alloy and may easily produce a large displacement. However, the actuator element 2 may not exert large force easily, which is a problem. If the modulus of elasticity and element thickness of the actuator element 2 are increased, the load may be increased. However, the amount of displacement may be reduced proportionately.
In other words, it has been difficult to acquire a sufficient amount of displacement and sufficient load (generative force) for producing a good feel of pushing when the key top 5 is pushed downward from the state in FIG. 13A to the state in FIG. 13B.
Reference may be made to Japanese Unexamined Patent Application Publication Nos. 2006-166638, 2005-27444, 2007-28749, and 2007-118159.
The inventions of the aforementioned patent documents have problems of the difficulty to acquire a good feel of pushing and their complicated structures resulting in larger element structures.